Work Energy and Power - Result Question 64

67. A metal ball of mass 2kg moving with a velocity of 36km/h has a head on collision with a stationary ball of mass 3kg. If after the collision, the two balls move together, the loss in kinetic energy due to collision is [1997]

(a) 140J

(b) 100J

(c) 60J

(d) 40J

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Answer:

Correct Answer: 67. (c)

Solution:

  1. (c) Applying conservation of momentum, m1v1=(m1+m2)v

v=m1v1(m1+m2)

Here, v1=36km/hr=10m/s

m1=2kg,m2=3kg v=10×25=4m/s

K.E. (. initial) =12×2×(10)2=100J

K.E. ( Final )=12×(3+2)×(4)2=40J

Loss in K.E. =10040=60J



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